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07-08-2014, 10:45 PM   #1
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K3 Autofocus

Apologies if this has been answered in an earlier thread but I need some advice/help on autofocus - and I don't find the K3 handbook much help.

For portraits, I'm finding that I will often get a sharp focus, but unfortunately not on the eyes. For other work, it all seems fine - landscapes, etc no problem.

My choice of lens is a Sigma 70mm, with a wide aperture to get a blurred background. What would be the best AF set up for such a portrait, that gives me sharp focus on the eyes even thought the sitter may be mobile??

07-08-2014, 10:54 PM   #2
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Try face detection live view AF. That's probably your best bet for a mobile subject; the next best would be spot AF.

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07-08-2014, 11:09 PM   #3
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Thanks Adam, for the quick response. I'll give LV a shot, although I prefer to use the viewfinder, so I'll try both.
07-08-2014, 11:27 PM   #4
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Shooting portraits since 2007 with K10, two K20's, two K5's and now two K5IIs, I use AF-S with a single center point. Focus where you want with rear AF, recompose and shoot. If I had other brands, I'd shoot the same way.

These two from last Friday, one of my favorite events, the no hands doughnut eating contest. Swinging doughnuts and moving kids. Manual exposure, 50-135 at 2.8, shutter 1/640, ISO 400 and 800 respectively. It was heavily shaded. First kid had a shaft of sunlight peeking through the trees, natures mono light.





07-08-2014, 11:39 PM   #5
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QuoteOriginally posted by regislea Quote
What would be the best AF set up for such a portrait, that gives me sharp focus on the eyes even thought the sitter may be mobile??
As Adam says, try shooting with Live View, making sure Face Detection is enabled (it should be on by default with the K-3).

If using the viewfinder, try settings like AF.C, focus priority selected, and then selecting a focus point close to the eye, whilst enabling 'Expanded Area AF (S)' to keep a tight track on the movement of the target AF point. [pp 42-46 of the K-3 manual].

For reference, the K-3'a AF point distribution looks like this:



Or just shoot as you would normally, but at f4 or f5.5 instead of f2.8. The extra DOF will solve your problem.

Also maintaining a tight focus on just one feature like the subjects eye, whilst shooting wide open, runs the risk of having the eye in focus, but the nose or lips out of focus. I've seen many portraits ruined by photographers giving priority to bokeh over focus depth when shooting portraits.

Last edited by rawr; 07-08-2014 at 11:47 PM.
07-08-2014, 11:49 PM   #6
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Thanks all for the instant help. Just tried two of the suggestions in poor lighting with a very mobile subject - my wife is getting very excited watching the Indonesian presidential election results coming in!

All work well but it seems the best result under those circumstances is the spot AF/viewfinder.

But Brooke/Rawr - I'll need to study yours further and try it out.

Thanks again.

Last edited by regislea; 07-09-2014 at 12:37 AM.
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